march:
Since the walls are not at 90˚ angles to each other, you need to decide how the roof will fit the walls:
1. Does each roof plan align with its parallel wall, so the ridge will be the bisecting angle of the two walls? Then place two single plane roofs on each wall and edit them at the ridge.
2. Is the roof a regular rectangular shape over the walls, with uneven eaves at the walls? Then use a Multilane roof aligned with one of he walls or the bisecting angle between the two walls.
You can also use the Rotate Orientation button at the bottom of the plan window to temporarily rotate the view if that helps.
David